<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <button>点击</button>
    <script>
        let btn=document.querySelector('button');
        function fn(){
            alert('aaa');
            btn.removeEventListener('click',fn);
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</html>